PROJECT SUMMARY Cigarette smoking contributes to nearly 30% of all cancer-related deaths.3 Menthol cigarettes comprise almost one-third of the U.S. market share and are disproportionately smoked by racial minorities.1 Tobacco control policies targeting menthol flavoring in tobacco could have significant public health outcomes, especially among black smokers. One key challenge of tobacco regulation is weighing the risks and benefits of potential policies across different populations (i.e., users and non-users).4 Tension arises between policies intended to prevent adolescent and young adult (AYA) tobacco initiation and those intended to reduce harm among current tobacco users. Specifically, menthol flavored e-liquid restrictions aimed at reducing AYA vaping may unintentionally discourage menthol cigarette smokers from switching to potentially less harmful products. E-cigarette use or vaping has increased dramatically among AYA and vaping devices with nicotine pods (e.g., JUUL) account for a large proportion of AYA use.5,6 These devices are available in many e-liquid flavors including menthol and mint, with mint being a popular flavor among AYA.2,7 The Food and Drug Administration and many states have announced intentions to limit all flavored e-liquids, including menthol and mint, in an effort to reduce AYA vaping. Alternatively, vaping devices, like JUUL, may be ideal substitution products for adult smokers who are unable to quit using nicotine. From a harm reduction perspective, moving smokers away from combusted tobacco (cigarettes) to non-combusted products (e-cigarettes) will likely result in a net positive public health impact.8 The availability of menthol e-liquids may be important for encouraging menthol cigarette smokers to switch to e- cigarettes, but mint e-liquids, which are appealing to AYA, may be unnecessary to facilitate switching. Including mint e-liquids in flavor bans but allowing menthol e-liquids to remain on the market as potential substitution products for menthol smokers may be an optimal policy approach. Behavioral economics is an ideal framework for answering this question because it applies economic constructs, such as product substitution, to individual decision-making. We are proposing a lab study and field assessment to determine how including menthol and mint e-liquids in e-liquid flavor bans or sales restrictions affects tobacco product purchasing and use among menthol cigarette smokers (N=80; 40 black, 40 white). At lab sessions, participants will complete the Experimental Tobacco Marketplace (ETM) task, a behavioral economics task in which they receive account balances to an online store and can buy menthol cigarettes at escalating costs or buy e-liquids, non-menthol cigarettes, or nicotine replacement gum at fixed costs. They will complete the task under three marketplace conditions: (1) only tobacco e-liquids available, (2) menthol and tobacco e-liquids available, and (3) menthol, mint, and tobacco e-liquids available. During a field assessment, product choice is validated by assessing use of products purchased during the ETM task. This proposal will inform policy-makers about the impact banning menthol and mint e-liquids will have on facilitating menthol cigarette smokers switching to e-cigarettes.